U.S. patent number 5,499,661 [Application Number 08/438,960] was granted by the patent office on 1996-03-19 for tube comprising composite layers with different modulii of elasticity.
This patent grant is currently assigned to Aerospatiale, Institut Francais du Petrole. Invention is credited to Marcel Auberon, Jacques Behar, Pierre Odru, Charles Sparks.
United States Patent |
5,499,661 |
Odru , et al. |
March 19, 1996 |
Tube comprising composite layers with different modulii of
elasticity
Abstract
A composite material tube, withstanding the internal pressure,
and comprising at least two layers of pressure reinforcement
fibers, or pressure resistant layers, wound at an angle at least
equal in absolute value to 70.degree., with respect to the center
axis of the tube. The two layers both undergo radial expansion
under an effect of the pressure, with one of these two layers being
inside the other. A circumferential modulus of elasticity of the
external layer is greater than the circumferential modulus of
elasticity of the internal layer.
Inventors: |
Odru; Pierre (Fontenay sous
Bois, FR), Sparks; Charles (Le Vesinet,
FR), Auberon; Marcel (Le Haillan, FR),
Behar; Jacques (Saint Medard en Jalles, FR) |
Assignee: |
Institut Francais du Petrole
(Rueil Malmaison, FR)
Aerospatiale (Paris, FR)
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Family
ID: |
9363781 |
Appl.
No.: |
08/438,960 |
Filed: |
May 11, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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794955 |
Nov 20, 1991 |
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631868 |
Dec 21, 1990 |
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318179 |
Mar 2, 1989 |
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Foreign Application Priority Data
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Mar 2, 1988 [FR] |
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88 02560 |
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Current U.S.
Class: |
138/124; 138/125;
138/153; 138/174; 138/130 |
Current CPC
Class: |
F16L
11/083 (20130101) |
Current International
Class: |
F16L
11/08 (20060101); F16L 009/16 () |
Field of
Search: |
;138/129,130,132,133,134,172,174,125,126,127,124,153,176,DIG.2,DIG.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bryant, III; James E.
Attorney, Agent or Firm: Antonelli, Terry, Stout &
Kraus
Parent Case Text
This is a Continuation Application Ser. No. 07/793,955, filed Nov.
20, 1991 now abandoned; which is a Continuation Application of U.S.
Ser. No. 07/631,868, filed Dec. 21, 1990 (now abandoned); which is
a Continuation of U.S. Ser. No. 07/318,179, filed Mar. 2, 1989 (now
abandoned).
Claims
What is claimed is:
1. A hollow tube comprising:
means for transferring or storing water or hydrocarbons under
pressure, the means for transferring or storing having an interior
surface for contacting the water or hydrocarbons under pressure and
an exterior surface separated by a wall thickness with the interior
surface being subjected to the pressure of the water or
hydrocarbons in a radially outward direction from a center of the
means for transferring or storing;
a plurality of pressure resisting means for resisting the radial
outward pressure of the water or hydrocarbons on the means for
transferring or storing, each pressure resisting means having an
interior surface and an exterior surface separated by a wall
thickness, an innermost pressure resisting means having its
interior surface in surface contact with the exterior surface of
the means for transferring or storing and an exterior pressure
resisting means being located farthest from the center of the means
for transferring or storing;
at least one tractive force resisting means for resisting tractive
forces applied to the hollow tube along a longitudinal axis of the
tube, each tractive force resisting means having an interior
surface and an exterior surface separated by a wall thickness with
each tractive force resisting means being disposed between a pair
of the plurality of pressure resisting means with the interior
surface of each tractive force resisting means being in surface
contact with an exterior surface of a different one of the
plurality of the pressure resisting means and the exterior surface
of each of tractive force resisting means being in surface contact
with an interior surface of a different one of the pressure
resisting means; and wherein
each of the plurality of pressure resisting means comprises a fiber
coated with a matrix to form a composite and is wound at an angle
greater than 70.degree. with respect to a longitudinal axis of the
tube, each of the at least one tractive force resisting means
comprises a fiber coated with a matrix to form a composite and is
wound with an angle between 0.degree. and 30.degree. with respect
to the longitudinal axis of the tube, a circumferential modulus of
elasticity of the exterior pressure resisting means is greater than
a circumferential modulus of elasticity of internal pressure
resisting means and any pressure resisting means disposed between
the innermost and the exterior pressure resisting means has a
circumferential modulus of elasticity which is between the
circumferential modulii of elasticity of the innermost and exterior
pressure resisting means and the means for transferring or storing
has a circumferential modulus of elasticity which is greater than a
circumferential modulus of elasticity of each pressure resisting
means which is inside of the exterior pressure resisting means.
2. A hollow tube in accordance with claim 1 wherein:
the means for transferring or storing includes a material chosen
from the group consisting of thermoplastics, aluminum, titanium and
steel.
3. A hollow tube in accordance with claim 1 wherein:
the fiber of the pressure resisting means is chosen from the group
consisting of glass, carbon and aramid fibers.
4. A hollow tube in accordance with claim 2 wherein:
the fiber of the pressure resisting means is chosen from the group
consisting of glass, carbon and aramid fibers.
5. A hollow tube in accordance with claim 1 wherein:
the fiber of each of the pressure resisting means, disposed in a
layer inside of a layer containing the exterior pressure resisting
means, has a longitudinal Youngs modulus approximately between
80,000 and 140,000 MPA; and
the fiber of the exterior pressure resisting means has a
longitudinal Youngs modulus approximately between 200,000 and
300,000 MPA.
6. A hollow tube in accordance with claim 2 wherein:
the fiber of each of the pressure resisting means, disposed in a
layer inside of a layer containing the exterior pressure resisting
means, has a longitudinal Youngs modulus approximately between
80,000 and 140,000 MPA; and
the fiber of the exterior pressure resisting means has a
longitudinal Youngs modulus approximately between 200,000 and
300,000 MPA.
7. A hollow tube in accordance with claim 3 wherein:
the fiber of each of the pressure resisting means, disposed in a
layer inside of a layer containing the exterior pressure resisting
means, has a longitudinal Youngs modulus approximately between
80,000 and 140,000 MPA; and
the fiber of the exterior pressure resisting means has a
longitudinal Youngs modulus approximately between 200,000 and
300,000 MPA.
8. A hollow tube in accordance with claim 4 wherein:
the fiber of each of the pressure resisting means, disposed in a
layer inside of a layer containing the exterior pressure resisting
means, has a longitudinal Youngs modulus approximately between
80,000 and 140,000 MPA; and
the fiber of the exterior pressure resisting means has a
longitudinal Youngs modulus approximately between 200,000 and
300,000 MPA.
9. A hollow tube in accordance with claim 1 wherein:
the fiber of at least one of the internal pressure resisting means
is glass fiber and the fiber of the external pressure resisting
means is aramid fiber.
10. A hollow tube in accordance with claim 2 wherein:
the fiber of at least one of the internal pressure resisting means
is glass fiber and the fiber of the external pressure resisting
means is aramid fiber.
11. A hollow tube in accordance with claim 5 wherein:
the fiber of at least one of the internal pressure resisting means
is glass fiber and the fiber of the external pressure resisting
means is aramid fiber.
12. A hollow tube in accordance with claim 8 wherein:
the fiber of at least one of the internal pressure resisting means
is glass fiber and the fiber of the external pressure resisting
means is aramid fiber.
13. A hollow tube in accordance with claim 6 wherein:
a ratio of the wall thickness of one of the internal pressure
resisting means to the external pressure resisting means ranges
between 0.15 and 0.60.
14. A hollow tube in accordance with claim 2 wherein:
a ratio of the wall thickness of one of the internal pressure
resisting means to the external pressure resisting means ranges
between 0.15 and 0.60.
15. A hollow tube in accordance with claim 3 wherein:
a ratio of the wall thickness of one of the internal pressure
resisting means to the external pressure resisting means ranges
between 0.15 and 0.60.
16. A hollow tube in accordance with claim 4 wherein:
a ratio of the wall thickness of one of the internal pressure
resisting means to the external pressure resisting means ranges
between 0.15 and 0.60.
17. A hollow tube in accordance with claim 5 wherein:
a ratio of the wall thickness of one of the internal pressure
resisting means to the external pressure resisting means ranges
between 0.15 and 0.60.
18. A hollow tube in accordance with claim 6 wherein:
a ratio of the wall thickness of one of the internal pressure
resisting means to the external pressure resisting means ranges
between 0.15 and 0.60.
19. A hollow tube in accordance with claim 7 wherein:
a ratio of the wall thickness of one of the internal pressure
resisting means to the external pressure resisting means ranges
between 0.15 and 0.60.
20. A hollow tube in accordance with claim 8 wherein:
a ratio of the wall thickness of one of the internal pressure
resisting means to the external pressure resisting means ranges
between 0.15 and 0.60.
21. A hollow tube in accordance with claim 9 wherein:
a ratio of the wall thickness of one of the internal pressure
resisting means to the external pressure resisting means ranges
between 0.15 and 0.60.
22. A hollow tube in accordance with claim 10 wherein:
a ratio of the wall thickness of one of the internal pressure
resisting means to the external pressure resisting means ranges
between 0.15 and 0.60.
23. A hollow tube in accordance with claim 11 wherein:
a ratio of the wall thickness of one of the internal pressure
resisting means to the external pressure resisting means ranges
between 0.15 and 0.60.
24. A hollow tube in accordance with claim 12 wherein:
a ratio of the wall thickness of one of the internal pressure
resisting means to the external pressure resisting means ranges
between 0.15 and 0.60.
25. A hollow tube in accordance with claim 1 wherein: the angle of
winding of the fiber of at least one of the pressure resisting
means is greater than 85.degree..
26. A hollow tube in accordance with claim 2 wherein: the angle of
winding of the fiber of at least one of the pressure resisting
means is greater than 85.degree..
27. A hollow tube in accordance with claim 3 wherein: the angle of
winding of the fiber of at least one of the pressure resisting
means is greater than 85.degree..
28. A hollow tube in accordance with claim 5 wherein: the angle of
winding of the fiber of at least one of the pressure resisting
means is greater than 85.degree..
29. A hollow tube in accordance with claim 9 wherein: the angle of
winding of the fiber of at least one of the pressure resisting
means is greater than 85.degree..
30. A hollow tube in accordance with claim 13 wherein: the angle of
winding of the fiber of at least one of the pressure resisting
means is greater than 85.degree..
31. A hollow tube in accordance with claim 1 wherein: the blowout
pressure is between 50 and 100 MPA.
32. A hollow tube in accordance with claim 2 wherein: the blowout
pressure is between 50 and 100 MPA.
33. A hollow tube in accordance with claim 3 wherein: the blowout
pressure is between 50 and 100 MPA.
34. A hollow tube in accordance with claim 5 wherein: the blowout
pressure is between 50 and 100 MPA.
35. A hollow tube in accordance with claim 9 wherein: the blowout
pressure is between 50 and 100 MPA.
36. A hollow tube in accordance with claim 13 wherein: the blowout
pressure is between 50 and 100 MPA.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a new composite tube structure
withstanding high pressures. Compared with tubes taught in the
prior art the tubes of the invention have either a lower thickness
and weight for equal service pressure, or a higher admissible
pressure for equal thickness.
The invention further provides examples of economically optimized
tubes.
By composite material should be understood a material formed from
parallel fibers, such as type E or R glass fibers, carbon fibers,
aramide fibers of Kevlar 29 or Kevlar 49 type (trademarks
registered by Du Pont de Nemours) coated with a matrix such as a
thermoplastic or heat hardenable material, for example, an epoxy
resin. This matrix adheres to the fibers.
The invention applies, in particular, to the construction of tubes
for transferring or storing fluids under pressure, such as water or
hydrocarbons.
More particularly, the tubes of the invention are well adapted to
be used in offshore oil working and search operations, for example,
as safety lines for upgoing or downgoing standpipes connecting the
bottom of the sea to a surface support such as a drilling or
working platform, or such as a subsurface buoy. These standpipes
are currently called risers. In the present text by composite
monolayer should be understood as the juxtaposition and possibly
superimposition of parallel fibers coated with a matrix. In the
case of a tube, these fibers are wound at the same angle with
respect to the axis of the tube.
By composite layer is meant either a monolayer, or the
juxtaposition and possibly superimposition of fibers in two
directions symmetrical with respect to an axis, these fibers being
coated with a matrix. In the case of a tube, the fibers are wound
at two opposite angles with respect to the axis of the tube.
By balanced composite layer is meant a layer comprising fibers
disposed in two directions, with equal distribution of the fibers
in these two directions.
The matrix adheres to the fibers. When a tube is formed from
several composite layers, the matrix forms a continuous medium
through these fibers to which it adheres, making the tube rigid. In
the rest of this text, unless otherwise stated, the term layer will
implicitly designate a composite layer.
The invention consists in winding substantially circumferentially,
on a starting tube, a composite material having a circumferential
modulus of elasticity higher than that of the internal,
substantially circumferentially wound pressure resistant
layers.
By circumferential modulus of elasticity of a composite layer wound
on a tube is meant the modulus of elasticity (or Young's modulus)
in a direction tangential to the layer considered, this tangent
being situated in a plane perpendicular to the axis of the
tube.
Composite tubes generally comprise superimposed fiber layers. As
was mentioned above, in each layer these fibers are disposed at
equal angles or angles symmetrical with respect to the axis of the
tube and embedded in a matrix. This matrix adheres to the fibers of
the different layers.
The invention applies more particularly, but not exclusively, to
tubes whose layers, which only withstand, albeit completely,
tractive forces are distinct from those which withstand
substantially, albeit completely, pressure forces. The matrix
coating the fibers of the different layers nevertheless forms a
continuous medium through these fibers. The traction resistant
layers comprise fibers wound at one or more small angles with
respect to the axis of the tube. Similarly, the pressure resistant
layers comprise fibers wound at high angles with respect to the
axis of the tube. Without departing from the scope of the
invention, instead of tubes comprising an external circumferential
layer whose circumferential modulus of elasticity is greater than
that of an internal layer, a pressure resistant casing may be
formed from a composite material, such as a reservoir, comprising
an external circumferential layer whose circumferential modulus of
elasticity is greater than that of an internal layer.
SUMMARY OF THE INVENTION
The present invention provides a composite material tube,
withstanding internal pressure and comprising at least two layers
of pressure reinforcement fibers, or pressure resistant fibers,
wound at an angle at least equal in absolute value to 70.degree.
with respect to the axis of the tube, the two layers both having a
radial expansion under the effect of the pressure, one of these two
layers being inside the other which is external thereto. This tube
is characterized particularly in that the circumferential modulus
of elasticity of the external layer is greater than the
circumferential modulus of elasticity of the internal layer.
Preferably, no composite layer withstanding the internal pressure
situated below the external layer withstanding the internal
pressure may have a circumferential modulus of elasticity greater
than that of the external layer.
When the tube comprises an intermediate pressure resistant layer
inserted between the internal and external layers, the
circumferential modulus of elasticity of the intermediate layer may
be between the circumferential modulii of elasticity of the
internal and external layers or equal thereto.
The angle of the pressure reinforcement layers may be at least
equal to 80.degree. or better at least equal to 85.degree.. The
angle of these layers will be preferably close to 90.degree..
The internal pressure resistant layer may comprise reinforcement
fibers whose longitudinal Young's modulus is close to 80 000 MPA,
such as glass fibers, and the external pressure resistant layer may
comprise reinforcement fibers whose longitudinal Young's modulus is
close to 140 000 MPa, such as the Kevlar 49 and the ratio of the
thickness of the internal pressure resistant layer to that of the
external pressure resistant layer may be between 0.20 and 0.50 or
even 0.60.
The internal pressure resistant layer may comprise reinforcement
fibers whose longitudinal Young's modulus is close to 140 000 MPa,
such as the Kevlar 49 fibers, and the external pressure resistant
layer may comprise reinforcement fibers whose longitudinal Young's
modulus is substantially between 200 000 and 300 000 MPa, such as
carbon fibers and the ratio of the thickness of the internal
pressure resistant layer to that of the external pressure resistant
layer may be in the range 0.15-0.30.
The tube may comprise at least one tractive force resistant
layer.
The fibers of the external pressure resistant layer may be
pre-stressed under traction, in the absence of pressure inside the
tube.
The tube may also comprise at least two layers of tractive force
resistant reinforcement fibers distributed throughout the thickness
of said tube.
The tube of the invention may be used for forming pipes whose
blow-out pressure is close to or higher than 100 MPa for
transferring or storing fluids.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be well understood and its advantages will be
clear from the following description of a few embodiments one of
which is illustrated in the accompanying Single Figure which is an
isometric view of a composite material tube to which the invention
is applied.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference 1 designates an internal sealed sheath of the tube. This
internal sealed sheath 1 may be made from elastomer, from a
thermoplastic or heat hardenable material such as BUNA, RILSAN
(which are respectively trademarks registered by HOECHST and AT
CHEM).
This internal sheath 1 may also be made from aluminium, titanium or
steel. The modulus of elasticity of these materials being generally
greater than that of the internal pressure resistant layers, these
types of internal sheaths undergo plastic deformation. On the
internal sheath 1 are wound several layers 2, 3, 4, 5, 6, 7, 8 of
composites. The internal layer 2 is preferably made from fibers
wound at an angle close to 90.degree. in absolute value, with
respect to the longitudinal center axis of the tube, so that this
internal layer 2 takes up essentially the pressure forces due to
the pressure prevailing inside the tube.
Layer 3, which takes up essentially the tractive forces which are
exerted along the axis of the tube comprises fibers wound at small
angles with respect to the axis of the tube, such as angles between
0.degree. and 35.degree., e.g 20.degree.. Layer 4 is a second
internal pressure resistant layer and is formed like layer 2 from
the same composite material, the fibers being wound as for the
internal layer 2 at the same angle with respect to the longitudinal
center axis of the tube. Thus, this layer 4 has the same
circumferential modulus of elasticity as layer 2. Without departing
from the spirit of the present invention, layer 4 may have a
circumferential modulus of elasticity greater than the modulus of
elasticity of layer 2, but less than or equal to that of the layers
which are external thereto and which withstand the internal
pressure.
Layer 5, like layer 3, is a layer withstanding the tractive forces
exerted on the tube. The intermediate pressure resistant layer 6
comprises reinforcement fibers wound at an angle close to
90.degree. with respect to the axis of the tube. This intermediate
layer 6 may be formed from a composite material different from that
used for layers 2 and 4. This difference of composite material may
be obtained, for example, by changing the respective matrix and
fiber proportions or by changing the nature of the fibers, or else
by changing the nature of the matrix. What matters in the present
invention is that the circumferential modulus of elasticity of the
pressure resistant layers which are internal thereto is at most
equal to that of the pressure resistant layers which are external
thereto.
Layer 7, like layers 3 and 5, is adapted to take up the tractive
forces exerted on the tube.
The external layer 8 is formed from resistant fibers wound at an
angle close to 90.degree. in absolute value, with respect to the
longitudinal center axis of the tube, so as to take up the forces
due to the pressure inside the tube. This external layer 8 is made
from a composite material having a circumferential modulus of
elasticity greater than that of the pressure resistant layers which
are internal thereto.
The intermediate layer 6 may have a circumferential modulus of
elasticity equal to that of layer 8 or equal to that of layer 4 or
intermediate those of layers 4 and 8.
The invention will be well understood from the following
example:
This example concerns the construction of a type having a service
pressure between 50 and 100 MPa with a safety coefficient of 2,
conferring thereon a theoretic maximum blow-out pressure of the
order of 200 MPa. The wall of this tube comprises:
five layers of composite fiber-resin materials wound at a small
angle with respect to the axis of the tube and taking up the
tractive forces; these composite material layers are spread out
relatively homogeneously inside the wall;
a layer of composite glass fiber-resin materials having a winding
angle close to 90.degree. with respect to the axis of the tube,
this layer being disposed from the inside of the tube; and
a layer of composite Kevlar fiber-resin materials having a winding
angle close to 90.degree. with respect to the axis of the tube,
this layer being disposed externally to the glass fibers.
By way of indication, such a tube may have an internal radius of
5.3 cm and an external radius of 7.3 cm (thickness/external radius
ratio : 38; this phenomenon depends solely on the ratios and not on
the absolute values). The layers of longitudinal pressure resistant
composites represent a cumulative thickness of 0.66 cm and are
evenly spaced apart.
The circumferential composite layers, i.e. the pressure resistant
layers, represent a cumulative thickness of 1.34 cm.
The following table gives the maximum circumferential and radial
stresses calculated in the different internal glass-resin composite
layers on the one hand and external Kevlar-resin layers on the
other, as a function of their respective thicknesses, for an
internal pressure of 210 MPa. This table is only relative to
pressure resistant layers.
______________________________________ glass composite Kevlar
stresses composite ##STR1## MParadial MPacirc radialcircstresses
______________________________________ 100% -210 1050 -- -- 73%
-210 960 -45 900 60% -210 927 -68 923 48% -210 895 -91 953 36% -210
867 -117 1000 24% -210 840 -144 1060 12% -210 820 -175 1144 0% -219
1250 ______________________________________
The above table shows the radial and circumferential stresses of
the glass composite layer and of the Kevlar composite layer
expressed in MPa. The following phenomenon will then be noted: the
reinforcement of the glass layers by external Kevlar layers having
a higher circumferential modulus of elasticity causes, for equal
material thickness, a reduction of the maximum stresses, not only
in the glass but also in the Kevlar, and correlatively an increase
of the admissible stresses and of the blow-out and service
pressures of the tube.
Furthermore, the circumferential stresses induced in the Kevlar
pressure resistant layers may be higher, taking into the account
that the fact that the radial stresses are reduced.
Thus, if we accept for example that the maximum admissible stresses
are the same in the Kevlar composite and the glass composite, and
if we take for breakage criteria the maximum induced
circumferential stress alone, the optimum proportion is situated at
60% for which the corresponding stresses in the glass composite and
the Kevlar composite are identical. The gain in performance is then
of the order of 10% without changing the thickness of the tube.
If we take a combined criterion as resistance criterion, the
optimum proportion will be lower, probably of the order of 30% to
50%, with an induced gain in performance which may reach 15% to
20%.
In fact, at very high pressures, the material of the wall must
withstand the circumferential tractive forces and hydrostatic
compression : at 2100 bars (21 hbars of transverse radial
compressive stress on the composite), the criteria (Tsai-Hill)
indicate that the tractive force characteristics in the direction
of the fibers are considerably reduced. The reinforcement
considerably relieves the tractive stress on the internal fibers
which take up the maximum transverse compression and transfer this
tractive stress to the external more rigid fibers of the material
which are less loaded under transverse compression.
Without departing from the scope of the invention, the number of
pressure or tractive force resistant layers may be reduced or
increased and the distribution of these layers modified.
* * * * *